In medical X-ray imaging patients are X-ray examined either by means of a stationary X-ray imaging system being located typically in special designed X-ray laboratory rooms or by means of a movable X-ray imaging system. Movable X-ray imaging systems are frequently used if a patient is not transportable.
A stationary X-ray imaging system typically comprises a so-called bucky unit. A bucky unit is a box, which comprises a tray for an X-ray cassette, additionally an anti scatter grid and a so-called Automatic Exposure Control (AEC) unit. An anti scatter grid is used for instance for chest exposures in the intensive care department, especially for heavy patients. The grid improves the image quality significantly in particular for thick objects. The anti scatter grid can be optionally removed from the bucky unit. The AEC may be used for controlling an X-ray source in order to allow for optimally exposed images with and without an anti scatter grid.
A movable X-ray imaging system is usually operated by using a free cassette for detecting X-rays, which have traversed a non transportable patient under examination. A free cassette is typically positioned just below the patient.
U.S. Pat. No. 4,205,233 discloses an X-ray radiographic table, which comprises a bucky frame having a front opening through which a bucky unit respectively a bucky tray may be inserted into the frame. The bucky tray supports a cassette, which carries an X-ray sensitive film. The cassette is centered on the bucky tray between adjustable clamps and is adapted to be aligned with an X-ray source.
JP 2004-073356 A discloses radiographic equipment comprising (a) a grid detection means for detecting the presence and absence of the grid, (b) a fixing means for fixing the grid, (c) a fixing detection means for detecting the fixing state of the grid and (d) a posture change restriction means for restricting the operation of the posture change of the photographic equipment. The operation of the posture change restriction means may be controlled according to the detecting result of the grid detection means.
U.S. Pat. No. 6,850,597 B2 discloses an X-ray image photographing apparatus including an X-ray source and an X-ray detector. The X-ray image photographing apparatus further comprises a grid detecting means having a construction for detecting at least (a) the presence or absence of a grid, (b) the kind of the grid and (c) the presence or absence of the replacement of the grid. Further, the X-ray image photographing apparatus comprises an image processing system for image processing and outputting image data collected by the X-ray detector and a memory having stored a plurality of sets of image processing parameters for controlling the image processing system based on an output of the grid detecting means. The image processing starts from selecting a gain image.
EP 1 420 618 A2 discloses an X-ray imaging apparatus including an X-ray source and an X-ray detector on which a plurality of different types of grids are detachably mountable. The X-ray detector includes an automatic exposure control (AEC) unit, which detects the quantity of X-rays emitted from the X-ray generation means and outputs a signal based on the detected quantity. The X-ray imaging apparatus also includes control means controlling the X-ray generation means based on the signal output from the AEC detector, and correcting the AEC detector output according to the type of grid used.
There may be a need for providing X-ray equipment for increasing the reliability of the emitted radiation dose for X-ray imaging in particular for patients being not transportable.